Topic: MLS Gasket leak after top end build. Repair questions. Solved!!

[albertaboy]

Here's something I have posted on several occasions: the O-rings that are coming in many gaskets kits (the orange ones for the 2 oil passages) are not thick enough. They are also too soft for 60 PSI oil systems (durometer about 45), but work OK on engines with roller-bearing crankshafts (20 PSI max), like KZ1000 or certain Suzy engines.

Here's how to check:
The compressed head gasket should now be approximately 1mm thick in the composite sections, since it was already squished. Lay your O-rings in the cylinder holes (oil feeds) where they will live, then lay the head gasket in place on the cylinders, too. Then measure how far the O-rings stick up above the head gasket. Chances are, they don't, or not by much. The O-rings I have received in the last 6 gasket kits are 2.4mm thick, and the recess in the cylinders, plus the head gasket, is about 2.3mm thick (or deep, depending on how you think of it...). This only leaves 0.1mm of a too-soft O-ring to try to hold back 60 PSI of hot oil: ain't gonna happen, in short.

To complicate this, some head gaskets also don't compress far enough. They must be 0.85mm to 1.05mm thick when set under spec'd torque. When released after that, they spring back about 0.1mm (thicker), so keep that number in mind for the following tests.

The durometer of the O-ring should first be at least 60 to hold back 50 PSI of oil at 6-10% compression (of its thickness). If the recess is, for example, 2.2mm deep and the O-ring is 2.4mm thick, then the compression is: (0.2/2.4*100%)=8.33%. This means IF the O-ring is 60 durometer and IF the hole is 2.2mm deep, then it would hold back about 45 PSI of hot oil pressure.

That means: it will leak...

So...I started buying thicker O-rings in harder durometers, and now have a large collection of those orange ones that belong to Kawasaki engines, and not to SOHC4 engines. They will work in the bottom of these oil passages if those recesses are not too deep, but other than that, they really don't belong in these engines.

I have the O-rings in 11x2.5mm thickness (Honda's spec) and also in 10.8x2.6mm thickness (so they will fit in the diameter OK) to solve this problem. Let me know if you need some? The postage is probably more than the O-rings, though.

Or, check through the O-rings you may have lying around: find one that is at LEAST 0.3mm thicker than the depth of the (recess+head gasket) and is black in color (not orange and soft) and stiff. This will help.

Very interesting. Thank you!! as this is the first I've seen this info.  I am using part # 91310-426-000  that I got from my Honda Dealer parts counter rather than from a kit.     They're listed as a 11x2.5 but what I'd have to question the durometer of that part #.  My engine is definitely producing  60psi just at idle. 

I have just assembled with a different gasket. So I am unable to check the measurements you write about.  I may as well finish re assembly and give it a try. If it doesn't work, I have to put it away until next spring anyways- I find leaving anything disassembled for too long isn't good.  Or is it my memory that isnt good.....

[albertaboy]

I found o-rings,here the link,
http://www.cmsnl.com/products/o-ring-11x25_91303035000/#.VBVeJyWV0m8

Thanks Bert.  Looks like the same o-ring that I was able to get at the dealer.  91303-035-000 was replaced by 91310-426-000.  Any idea how hard these ring are? Any idea if this ring is too small to use with an MLS?

[bert96]

I bought two o rings from Hondarestoration.com

[albertaboy]

Good news that my head gasket is no longer leaking.
Re-cap - I set the MLS aside, put the gasket in that came with the Cruizenimage Ebay 836 piston set. Copper coated it, put all the dowels and packing o rings back in. After 25 miles or so... no evident leak at the head gasket.  That particular gasket/ oem o ring combo seems to work together a least.

But....
I do have some oil leaking from the plug recess area. I know it will either be the pucks or the from the cam tower studs which I thought I had sealed them really well. It's very small so I can live with it for a while.
The bigger leak I will need to deal with is from the crank seal behind the point plate.  I think I have to split the case... dont I. 

Thanks for everyone's help with this. Much appreciated.

[BPellerine]

now put a big warm jacket on and go!bill

[andrewk]

Here's something I have posted on several occasions: the O-rings that are coming in many gaskets kits (the orange ones for the 2 oil passages) are not thick enough. They are also too soft for 60 PSI oil systems (durometer about 45), but work OK on engines with roller-bearing crankshafts (20 PSI max), like KZ1000 or certain Suzy engines.

Here's how to check:
The compressed head gasket should now be approximately 1mm thick in the composite sections, since it was already squished. Lay your O-rings in the cylinder holes (oil feeds) where they will live, then lay the head gasket in place on the cylinders, too. Then measure how far the O-rings stick up above the head gasket. Chances are, they don't, or not by much. The O-rings I have received in the last 6 gasket kits are 2.4mm thick, and the recess in the cylinders, plus the head gasket, is about 2.3mm thick (or deep, depending on how you think of it...). This only leaves 0.1mm of a too-soft O-ring to try to hold back 60 PSI of hot oil: ain't gonna happen, in short.

To complicate this, some head gaskets also don't compress far enough. They must be 0.85mm to 1.05mm thick when set under spec'd torque. When released after that, they spring back about 0.1mm (thicker), so keep that number in mind for the following tests.

The durometer of the O-ring should first be at least 60 to hold back 50 PSI of oil at 6-10% compression (of its thickness). If the recess is, for example, 2.2mm deep and the O-ring is 2.4mm thick, then the compression is: (0.2/2.4*100%)=8.33%. This means IF the O-ring is 60 durometer and IF the hole is 2.2mm deep, then it would hold back about 45 PSI of hot oil pressure.

That means: it will leak...

So...I started buying thicker O-rings in harder durometers, and now have a large collection of those orange ones that belong to Kawasaki engines, and not to SOHC4 engines. They will work in the bottom of these oil passages if those recesses are not too deep, but other than that, they really don't belong in these engines.

I have the O-rings in 11x2.5mm thickness (Honda's spec) and also in 10.8x2.6mm thickness (so they will fit in the diameter OK) to solve this problem. Let me know if you need some? The postage is probably more than the O-rings, though.

Or, check through the O-rings you may have lying around: find one that is at LEAST 0.3mm thicker than the depth of the (recess+head gasket) and is black in color (not orange and soft) and stiff. This will help.

I've been buying those o-rings in 90 durometer, made for pressure washer use.  90 is almost too hard, but it works really well with HD studs.  Last MLS I put together was with stock studs, and I pinched one of the o-rings somehow in assembly, boy was that a leak.

[Chad]

Interesting thread. I just assembled my top-end using the kit from Cycle X with the MLS gasket. Now you've got me worried! Did you ever figure out why the MLS didn't work for you?

[albertaboy]

Interesting thread. I just assembled my top-end using the kit from Cycle X with the MLS gasket. Now you've got me worried! Did you ever figure out why the MLS didn't work for you?

I would check the o-ring/gasket measurements HondaMan wrote about.  I had already assembled when he posted so I decided to go ahead and test the different gasket out. I used Honda oem o-rings right from the start and not the kit o-rings he mentions, so admittedly, I wonder if the Honda oem o-rings are also too soft to be used with a MLS.  Sounds like sourcing harder o-rings would be worth your time to do a bit of dis-assembly, go back and put them in.   Besides that, with the MLS reputation, I have no real idea why it did not work.

[Chad]

Interesting thread. I just assembled my top-end using the kit from Cycle X with the MLS gasket. Now you've got me worried! Did you ever figure out why the MLS didn't work for you?

I would check the o-ring/gasket measurements HondaMan wrote about.  I had already assembled when he posted so I decided to go ahead and test the different gasket out. I used Honda oem o-rings right from the start and not the kit o-rings he mentions, so admittedly, I wonder if the Honda oem o-rings are also too soft to be used with a MLS.  Sounds like sourcing harder o-rings would be worth your time to do a bit of dis-assembly, go back and put them in.   Besides that, with the MLS reputation, I have no real idea why it did not work.

The gasket kit I got from Cycle X did come with the o-rings. I'll check to make sure they're thick enough per HondaMan's instructions. Thanks for the advice! I'll let you know how it goes 

[RobbyD]

After 400 miles on the top end rebuild on my 550 using the cycle x mls head gasket, mine developed a tiny leak.  Just enough to piss you off.  I'll deal with it the rest of the riding season we have left and throw on a regular head gasket this winter... 

[RobbyD]

I did not.  I was under the impression with the mls you didn't need to.  I'll take the valve cover off and check them all this weekend possibly

[RobbyD]

Very good to know, I didn't even consider stud stretch.  I will get on this this weekend.  The spot that is leaking is maybe the size of a pin tip and emits a tiny little streak of oil. 

Sucks to pull the valve cover but way better then a leaky head gasket.  Thanks calj